Thermal retarder



Oct. 7, 1947.

c. M. OSTERHELD THERMAL RETARDER Filed Sept. 20, 1944 3 Sheets-Sheet l I N V EN TOR. [40s rmwa 0 M7 5- GEAR/ BY ATTORNE Y Oct. 7, 1947. c. OSTERHELD 2,428,525

THERMAL RETARDER Filed Sept.- 20, 1944 3 Sheets-Sheet 2 j 7/ m Q o g 49 INVENTOR;

62 ARX 05 75mm 17 BY W ATTORNEY Patented Oct. 7, 1947 UNITED STATES PATENT OFFICE Clark M. OsterheId, Stoughton; to MoGraw Electric Company, poration of Delaware Wist, assignor' Elgin, 111., a cor- Application September 20, 1944, Serial No. 554,998

6 Claims. 1

My invention relates to electric heater control devices and particularly to thermal retarder Iheat'e'r control switch units.

b An object of my invention is to provide a relatively simple, inexpensive, easily manufactured, and properly operative structure to selectively cause immediate 'energization of the electric heater or a domestic hot water tank or ehergiza'tion -r6f the heater with a predetermined time delay in accordance with the amount of cold water in :the tank at the start of an 'oiT-pe'ak period.

Other objects of my invention will either be apparent from a description of two forms of devices embodying my invention or will be set but in the course of such description and particularly in the appended claims.

In the drawings,

Figure '1 is a vertical, sectional view through a domestic hot water tank having associated therewith a thermal retarder embodying my invention,

Fig, 2 is a diagram of electric connections showing the contacts in the positions occupied by them when the tank is full of cold water and the time switch is open.

Fig. 3 is a diagram of connections showing the contacts in the positions occupied by them when the tank is more than half full of hot water positioned in its top portion and containing'c'o'ld water in the bottom vportion, the time switch being closed as at the start or an off-peak period,

Fig. 4 is a diagram or connections including a modified form of thermal retarder shown particularly in-Figs. '9 to 12, the contacts being shown in this figure as when the tank is full of cold t r,

Fig. 5 is a top plan view of 'the first form of thermal retarder embodying my invention, the icover being shown in section with the contacts :"shown in the positions they occupy in Fig. 2,

t 'Fig. 6 is a horizontal, sectional View therethrough, taken on the line =6-6 of Fig. 7, with the contacts shown in the positions they occupy .in-Fig. 3.

7 is a view in side elevation of the thermal yretarder with the cover shown insection.

Fig. 8 is a view in front elevation thereof,'with th -cover' shown in section,

V, Fig. '9 is a top plan view of a modified form of thermal retarder shown in Figs. 10"and 11', with thecovershown-in section,

d Fig. 10 is a view inside elevation of a second form otthermal retarder. Fig. ll is a viewin front elevation of the device showninFigs. 9 andl-O, and

s Fig. 12 is anextendedplan vieWof the thermal element shown in Fig. 10 of the drawings.

Referring first of all to Fig. 1 of the drawings I have there shown an ordinary domestic hot water tank 2| having a lower cold water inlet pipe 23 an upper hot water outlet pipe 25, and having also a mass 2! of heat-insulating material located therearound, which mass is held in proper operative position around the tank 2! as by an outside casing 29.

I provide preferably, but not necessarily, a single electric heater 3|, which, if only a single electrio heater is provided, is located adjacent to the lower end portion of the tank 2| and may be located in a tunnel member 33. All of the hereinbefore described elements of an electric hot water heater are old and well known in the art and constitute no part of my present invention.

I provide a lower thermally 'actua'ble heater control switch designated in its entirety by numeral 3-5, and here also the showing is general only, since any other thermally-actua-bl'e switch structure effective for the same purpose may be used in placethereof. I have illustrated the thermally-'actuable switch 35 as comprising a bimetal bar 31, which has one end mounted on a contact 39, 'while the other end is adapted to engage another contact 4|, which contacts are insulatedly mounted on tank 2| adjacent the lower end thereof. The design, construction, and adjustment of the thermally-ac'tuable switch 35 is such that the bimetal bar 31 will be in closed position, that is in engagement with contact 41, when subject to cold water in the tank, and will be out of engagement therewith when subject to hot water. "When I speak of cold water, I refer to water the 'tem- 'p'eratureof which is on the order of to 79 and when I speak of hot water I refer to water temperature of which is on the order of or slightly higher.

I provide further a thermal retarder designated generally by numeral 43 and prefer to locate this thermal retarder heater control switch unit in heat-receiving relation on the tank at about onehalf of the height thereof.

Referring now to Figs. 5 to 8 inclusive, 1 have there illustrated the details of construction and mounting of the thermal retarder hi. -I provide a supporting block 45, whch is made of heatconducting material, and the inner surface of which is of ancuate shape so that substantially the entire inner surface of the block Will be in engagement with the outer surface of tank 2|,

seams 47.

I provide further a supporting bracket 49, which is of substantially L-shape and which has the its vertically-extending portion secured against support 45 as by machine screws 5|. The front surface of the vertically-extending portion of member 49 is provided with a projecting portion 52, which has secured to it the two side portions of a bracket 53, which side portions may be secured in proper operative position against portion 52 as by short machine screws 55.

I provide a block 57 of electric-insulating material which is secured against the side pieces 53 as by a plurality of small machine screws 59, a permanent horseshoe magnet 6| being also secured in proper operative position, as shown particularly in Fig. 7 of the drawings, by the machine screws 59. The block 51 has two recesses 63 and 65 in its upper surface to receive parts of the switching means. The portions of block 51 between the recesses 63 and 65 and at the right of recess 65 (as seen in Fig. 7) are provided with aligned openings therethrough to receive an actuating rod 61 which is adapted to be moved by a relatively long creep-type bimetal bar 59 having its lower end mounted on projection 52 as by a machine screw I I. The upper end of bimetal bar 69 may be made of U-shape to fit into the reduced end portion of rod 51, a pair of enlarged flanges 73 being provided.

The end portions of the permanent magnet 6| extend vertically upwardly, as shown particularly in Fig. '7 of the drawings, and a magnetic keeper I5 is fixedly mounted on rod 6'1 so that it will be in engagement with the vertical end portions of magnet when the bimetal bar 69 is subject to cold water in the tank. I provide further a contact bridging member 11, supported by a collar 18 of electric-insulating material, on rod 91, which bridging member is positioned in recess 65 and is adapted to engage with and be disengaged from two fixed contacts 19 and BI supported by block 51. Contact bridging member I1 is biased to the left as by a spring 83 positioned between bridging member I1 and a collar 85 fixedly mounted on rod 61. A second coil spring 81 is also mounted on rod 61 and extends to the right of collar 85 and against a screw bearing 89 which has screw-threaded engagement in an opening in the right hand portion of member '1. Contact member I9 has a second contact member 9 I electrically connected therewith and positioned at the left hand side of the outer end portion of member 51, while contact member 8| has electrically connected therewith a contact member 93 also positioned at the left hand side of the outer end portion of member 51 so that the contact bridging member 1! may operatively engage contact members 19 and 8| or contact members 9| and 93 in accordance with the position of the bimetal bar 69.

I provide a small heating coil 95 on the upper end of bimetal bar 69 so that while the lower end portion of the bimetal bar 69 is subject to the temperature of water in the tank, the upper end portion thereof is controlled particularly by the heating coil 95. A casing 96 is provided for the parts above described.

Bimetal bar 69 is shown, in full lines in Fig. '7, in the position which it will occupy when subject to cold water in the tank, so that contact bridging member 11 will be in engagement with contacts I9 and 8|, and keeper I5 will be in engagement with permanent magnet 6|.

When bimetal bar 09 is subject to hot water in the tank, the contact bridging member 11 is out of engagement with either pair of fixed contacts, and when heating coil 95 has been energized for say four hours, the bimetal bar 69 will have flexed in a clockwise direction to the position shown in broken lines and bridging member I1 will be in engagement with fixed contacts 9| and 93. The temperature of the free end of bimetal bar 69 will be on the order of 200 to 250 F. at this time.

Referring now to Figs. 2 and 3 of the drawings, I have there illustrated a diagram of connections of the assembled system, of which my just above described thermal retarder heater control switch unit is a part. I have shown a time-controlled switch designated generally by numeral 91 and comprising a pair of contact arms 99 and IOI. Contact arms 99 and |0| are designed and constructed to be out of engagement with each other during all on-peak periods of a twenty-four hour day, while they are to be in engagement with each other during off-peak periods of a twenty-four hour day, being controlled by a continuously-operative timer of any desired kind.

I provide a pair of supply circuit conductors I03 and I05, of which conductor I03 is connected with arm 99. Contact arm |0I is connected with fixed contact 93 by a conductor I01, and as has already been hereinbefore stated, contact 93 is electrically connected with contact BI. Contact BI is connected by a conductor I09 with one terminal of heating coil 95, the other terminal of which is connected by a conductor I II with contact 4| of the lower thermal switch 35. Contact 39 of lower thermal switch 35 is connected by a conductor I I3 with the second supply circuit conductor I05. Contact 19 is connected by a conductor I I5 to one terminal of heater 3 I, the other terminal of which is connected by a conductor III with contact II of the lower thermally-actuable switch 35,

Referring now particularly to Fig. 2 of the drawings, I have there shown the parts in the positions they will occupy when the tank is filled with cold water or is at least more than half full of cold water, and with the time switch in open position, as during on-peak periods. Bimetal bar 69 will have flexed to the position shown in full lines so that contact bridging member 11 is in engagement with contacts 19 and 8| by reason of the movement of rod 61 to the left compressing spring 83. Keeper I5 will also be in engagement with magnet 5|, as shown in Figs. 5 and '7. As soon as closure of the time-controlled switch 91 occurs, as at the start of an off-peak period, say 10 p. m., energization of the heater 3| will occur through a circuit as follows: from supply circuit conductor I03, engaged contact arms 99 and IN, conductor I01, to contacts 93 and 8|, through contact bridging member 11, to contact I9, through conductor 5, heater 3|, conductor II'I, through closed switch 35, and then through conductor I I3 to the second supply circuit; conductor I05. This will cause energization of heater 3| and heating up of the upper end portion of the cold water in the tank, with the result that at the end of say one or two hours, sufiicient hot water has been heated to the predetermined temperature of 150 or over to subject the thermal retarder unit to hot water, causing flexure in a clockwise direction of bimetal bar 69, with the result that contact bridging member I1 will be moved out of engagement with contacts 19 and 8|. The difference in temperature between hot and cold water is 90 to F., which is a rather large change of temperature to which the bimetal bar 69 is subjected. The bimetal bar will tend to flex in a clockwise direction with any increase of temperature of the contact bridging water in the tank, but the action of the keeper with the permanent magnet 6| will hold the member I1 in engagement with fixed contacts 19 and 8| until the temperature of bimetal bar 69 is substantially 150, when quick movement of the contact bridging member 11 out of engagement with contacts 19 and 8| will occur, whereby the heater 3| is deenergized.

At the same time an energizing circuit through the small heating coil 95 was closed as follows: from supply circuit conductor I03, through engaged contact arms 99 and. I 0|, conductor I01, contacts 93 and'BI, conductor I09, coil 95, conductor III, through closed switch 35, and from there through conductor II3 to the second supply circuit conductor I05. Energization of heating coil 95 is therefore controlled jointly by the time-controlled switch 91 and the lower thermally-actuable heater control switch 35. The electric energy translated into heat in heating coil 95 is such that it will require from four to six hours to cause temperature rise of particularly the upper end portion of bimetal bar 69 to cause full flexure of that part thereof in a clockwise direction and engagement of bridging member 11 with the second pair of contacts 9| and 93 causing reclosure of the energizing circuit through heater 3| substantially as hereinbefore described with the sole exception that contact bridging member is now in engagement with contacts 9I and 93, instead of with contacts '19 and 8|.

Heating coil 95 was energized at the same time as was electric heater 3| and caused a small increase in temperature of the outer free end of bar 09 in the one or two hours it will require to heat the water in the upper part of the tank or until the thermal retarder is subject to hot water. The adjustment of the thermal retarder unit is such that interruption of the energizing circuit of heater 3I will occur shortly after the thermal retarder is subject to hot water in the tank. The reenergization of heater 3I will therefore take place in from two to three hours after it was first deenergized and will continue until substantially all of the water in the tank is hot, at which time, assuming that this occurs before opening of the time-controlled switch takes place, the lower thermally-actuable switch 35 will move to open position, whereby heater 3| is deenergized.

Let it now be assumed that the amount of hot water withdrawn from the tank during on-peak periods was less, so that only the lower thermally-actuable switch 35 was subject to cold water and the parts of the thermal retarder were in the positions shown in Figs. 3 and 6. In this case, when the time-controlled switch 91 was closed, the hereinbefore described energizing circuit through heating coil 95 Was closed immediately upon closure of the time-controlled switch 91, with the result that, in say four hours, after the start of an oiT-peak period, bimetal bar 69 will have been flexed in a clockwise direction from the position shown in Fig. 3 of the drawings, so that contact bridging member I1 will be moved into engagement with contacts 9| and 93, whereupon the hereinbefore described energizing circuit through heater 3| will be closed, this energization continuing until substantially all of the water in the tank is hot, when thermally-actuable switch 35 will open the circuit, if this occurs before opening of the time-controlled switch.

The above described interruption of the circuit by the lower thermally-actuable switch 35 may, however, not occur, deenergization of heater 3| being effected by the opening of the time-controlled switch 91 at the end of in case less than substantially all of the water in the tank is hot by that time.

Referring now to Figs. 9 to 12, I have there illustrated a modification of a thermal retarder heater control switch unit slightly difierent than the device shown in Figs. 5 to 8 inclusive. I provide a heat-conducting supporting block IZI, which is provided with an arcuate inner surface so that all of this surface will be in heat-conduct.- ing engagement with the outer surface of tank 2|, and block I2I may be secured and held in proper operative position as by welding seams I23. I provide a bracket I25, which may be of substantially L-shape, with its vertical portion held as by short machine screws I21 against block I2 I.

I provide a creep-type bimetal bar I29, which is normally of substantially U-shape and mounted against a front projecting portion I 3| of bracket I25 as by a bar I33 held by machine screws I35 against projection I3I. The high-expansion component of bimetal bar I29 is upon the inside of the bar when bent to U-shape, and I reduced area at bar I29 and support the bar against projection I3I adjacent to portion I31 by the inner end portion of bimetal bar I29.

I provide a resilient bar I39, which is secured to the upper end of the inner portion of bimetal bar I29, and mount thereon a contact bridging member III, a sheet I43 of electric-insulating material being provided to properly electrically insulate the contact bridging member I4I from bar I39. Contact bridging member I4I is adapted spaced fixed contacts I45 mounted on a block I49 of electric-insulating inaterial, which is held by a supporting bracket I5I, which is secured against the upper end portion of bracket I25 as by machine screws I53.

The second outer end portion of bimetal bar I 29 has insulatedly mounted thereon, adjacent its outer free end portion, a heating coil I55, the

of 200 F. to 250 F., to cause flexure in a clockwise direction sufiicient to cause a contact bridging member carried thereby to engage fixed contact members, will require from four to six hours. The portion I31 of reduced area of cross section tends to prevent or retard the flow of heat from the one to the other end portion of bimetal bar I29. A resilient bar I51 is secured to the outer end of the outer portion of bimetal bar I29 and has insulatedly mounted thereon a contact bridging member I 59, which is adapted to engage with and be disengaged from a second pair of fixed contacts IOI and I63, which are respectively electrically connected with contact members I45 and I 41 hereinbefore described. A cover I64 is also provided.

Referring now to Fig. 4.- of the drawings, I have there illustrated a diagram of connections of an electric circuit embodying the thermal retarder switch unit shown in Figs. 9 to 12 inclusive. The parts are shown in Fig. 4 of the drawings, as when the tank is slightly more than half full of cold water, when the left hand or inner portion of bimetal bar I29 will be in position to cause contact bridging member IM to engage contacts I45 and I49 to cause energization of the heater 3| through a circuit as follows: from supply circuit conductor I03, through closed time switch 91, a conductor I65 to contact I49, through bridging an off-peak period member IM to contact I45, through a conductor I61 to heater 3|, through a conductor M1 to the closed lower thermally-actuable switch 35, and from there through conductor M3 to the other supply circuit conductor I05. This energizing circuit will be established by the closing of time switch 91, and energization of the heater 3| will continue until substantially one-half of the water in the tank is hot, which will require from one to two hours.

Energization of heating coil |55 began also with the closing of time switch 91, and this energization continued irrespective of deenergization of heater 3| as above described. In about four hours the temperature of the outer or right hand portion or" bar E29 will have reached a value on the order of 200 to 250 F., causing flexure of this portion in a clockwise direction and engagement of bridging member 159 with contacts IBI and I53, whereby heater 3| is reenergized through a circuit as follows: from supply circuit conductor I03, through closed switch 91, conductor I65, contact F53, bridging member I59, contact IEI, conductor I81, heater 3|, conductor 1, closed switch 35 and through conductor 3 to the other supp-1y circuit conductor I05. This energization will continue until substantially all of the water in the tank is hot, when switch 35 will open, that is, if all of the water is not before the end of an off-peak period. If less than all of the water in the tank is hot by the end of the off-peak period, the heater and system will be deenergized by opening of the time switch.

In case only a relatively small amount of hot water was withdrawn from the tank during onpeak periods, so that the bimetal bar I29 of the thermal retarder unit was subject to hot water in the tank, with the result that contact bridging member Hi l was out of engagement with contacts I45 and I49, then an energizing circuit through heating coil I55 will be established at the start of an ofi-peak period as follows: from supply circuit conductor I03 through closed switch 91, conductor E65 to contact I63, through a conductor lfid, heating coil I55, conductor |1|, to closed lower thermal switch 35, and from there through conductor IIS to the second supply circuit conductor E05. The heating coil I55 thus energized, will cause flexure of the second or outer end portion of bimetal bar I29 in a clockwise direction, so that when a predetermined high temperature, on the order of 200 to 250 F., has been reached, the outer end portion of bimetal bar I29 will have flexed enough to cause engagement of contact bridging member I59 with contacts ISI and E53, whereby an energizing circuit through heater 3| is established, including contact bridging member I59 and engaged contacts IBI and E83. Energizaticn of heater 3| will continue until substantially all of the water in the tank is hot, assuming that all of it will be heated before opening of the time-controlled switch 91, when lower thermally-actuable switch 35 will move to open position and deenergize the heater 3|. If, for any reason, less than all of the water in the tank is hot by the end of an off-peak period, then heater 3! will be deenergized by opening of the time-controlled switch 91.

The thermal retarder shown in two forms is therefore effective to selectively cause either immediate energization of an electric heater for a hot water tank upon closure of a time-controlled switch, or with a predetermined time period of delay after closure of a time-controlled switch, in accordance with the amount of hot water in the tank at the time of closure of the time-coritrolled switch.

The use of permanent magnet 5| and spring 81 permits of holding the contact bridging member 11 in engagement with fixed contacts 19 and BI until the temperature of bimetal bar is on the order of F. and to hold it out of engagement with fixed contacts 9| and 93 until the temperature of bimetal bar is on the order of 250 F. The use of the spring bars I39 and I51 serves the same purpose, namely that of ensuring engagement and disengagement of the contact bridging members with the fixed contacts at the desired temperatures. Th permanent magnet is also effective to cause a quick break between bridging member 11 and contacts 19 and 8|. The tension of spring 81 may be varied by screw bearing 89, to permit of manual adjustment of the time element in which bridging member 11 engages contacts 9| and 93, as well as of the temperature at which such engagement occurs.

Various modifications may be made in the device embodying my invention, and all such modifications clearly coming within the scope of the appended claims shall be considered as being covered thereby.

I claim as my invention;

1. A thermal retarder switch unit for a hot water tank heater, comprising a tank, a bimetal bar, one end portion of which is adapted to be mounted in heat-receiving relation on a tank, a heating coil mounted on the other end portion of said bimetal bar, switching means including a pair of fixed, spaced, electrically-connected contacts, the bimetal bar closing a heater energizing circuit through the first of said fixed contacts when subject to cold water in the tank, opening said heater-energizing circuit when subject to hot water in th tank and when the heating coil is unenergized and closing a heaterenergizing circuit through the other fixed contact when the bar is subject to hot water in the tank and the heating coil has been energized for at least a predetermined period of time.

2. A thermal retarder switch unit for controlling a hot water storage tank heater circuit, comprising a circuit including a bimetal bar having one end portion adapted to be mounted in heat-receiving relation on a tank, a heating coil mounted on the other end portion of said bimetal bar, contact members carried by and actuable by said bimetal bar and a plurality of fixed, spaced, electrically-connected contacts in said circuit, the bimetal bar effecting closure of said circuit through the first of said fixed contacts when subject to cold water in a tank, effecting opening of said circuit when subject to' hot water in a tank and when said heating coil has been energized for less than a predetermined period of time and efiecting reclosure of said circuit when subject to hot water in a tank and when said heating coil has been energized for at least a predetermined period of time.

3. A thermal retarder switch unit for a hot water storage tank heater circuit, comprising a circuit including a bimetal bar, one end portion of which is mounted in heat-exchanging relation on a tank, a heating coil on the other end portion of said bimetal bar and a plurality of cooperating fixed contact members in said circuit, the bimetal bar closing said circuit through certain of said contact members when subject to cold Water in a tank, disengaging said certain contact members when subject to hot water in 9 a tank and reclosing said circuit through other of said contact members when said heating coil has been energized for a predetermined length of time.

4. A thermal retarder heater control switch unit for a hot water storage tank heater, comprising a bimetal bar of substantially U-shape, a supporting block of heat-conducting material secured to one end portion of said bar and adapted to be secured in heat-receiving relation on a tank, a heating coil for the other end portion of said bimetal bar and means for reducing the flow of heat between the two end portions of said bimetal bar.

5. A thermal retarder heater control switch unit for a hot water storage tank heater, comprising a bimetal bar of substantially U-shape, a supporting block of heat-conducting material secured to one end portion of said bar and adapted to be secured in heat-receiving relation on a tank, a heating coil for the other end portion of said bimetal bar, the intermediate part of said bar being of reduced area of cross-section to reduce the flow of heat between the end portions of the bar.

6. A thermal retarder switch unit for a hot water storage tank heater, comprising in combination with a tank a creep-type bimetal bar, means for connecting one end portion of said bar for heat exchange with water in the tank, a heating coil mounted on the other end portion of said bar, contact members carried by the ends of said bar and a plurality of fixed, spaced, electrically-connected contacts adapted to be selectively engaged by the respective contact members carried by the ends of said bar in predetermined sequence in accordance with the temperature of said ends of the bar.

CLARK M. OSTERHELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,175,827 Conklin Oct. 10, 1939 2,272,064 Kirkpatrick Feb. 3, 1942 2,330,161 Townsend Sept. 21. 1943 2,331,737 Scoggin Oct. 12, 1943 

